1. Field of the Invention
The invention pertains to a strip-casting machine with two casting rolls.
2. Description of the Related Art
It is known that twin-roll strip-casting machines can be used to produce strips continuously from a molten metal bath, especially from molten steel. The molten metal is supplied continuously in this case to the casting gap defined by two driven casting rolls. Molten metal solidifies upstream of and in the gap, and a strip which is at least partially solidified is conveyed out of the gap by the casting rolls. This strip can then be subjected to additional continuous or discontinuous operations such as cooling, reheating, hot- or cold-rolling, shaping into sections, hardening and tempering of the surface, trimming, etc.
It is also known that, in strip-casting machines with two casting rolls set up essentially parallel to each other, the casting gap can also be limited by two side plates on the roll sides. These side plates are set elastically against the end surfaces of the barrels of the two casting rolls by setting devices. The casting rolls and usually also the two setting devices for the side plates are supported on a standard. When strips are cast, especially steel strips, the side plates are worn down by abrasive wear as a result of the friction with the casting rolls and also, in the lower part, as a result of the friction with the solidified strip. When thus worn out, they must be replaced during a halt in the casting operations. To accomplish such replacement, the side plates are moved out of the casting position, in which the plates are resting against the barrels, in an essentially horizontal direction by the setting devices and thus away from the barrels and into a setting position. The plates are then moved upward from the setting position by means of small plate-changing devices, e.g., robots, which are mounted on the casting platform on each side of the machine (compare Japanese Patent Disclosure JP-5 [1993]-329,583 A). Then the side plates are set down onto a cart and brought to the side plate renovation shop. After a renovated side plate has been preheated, it is picked up by the robot and brought into the setting position from above and attached to the machine. When such robots are provided on both sides of the machine near the standard, they block access to the strip-casting machine. When the robots are set up 2-3 m away from the standard, the size and bulk of the robots increase correspondingly, and the side plates can no longer be moved into the setting position with precision. In addition, before the side plates are set down on the standard, all the supply lines such as those for heating and cooling, electric power lines, pressure media lines, etc., must be disconnected. The installation and removal of the side plates by means of robot arms, etc., requires that the robot arms have unhindered access to the side plates when they are in the setting position. This free access makes it difficult to enclose the casting machine so that an inert gas atmosphere can be created to keep oxygen from coming in contact with the steel strip and the cast strip.
Strip-casting machines with 2 casting rolls have been built with casting roll diameters of 50-1,500 mm. In strip-casting machines with a casting roll diameter of more than 800 mm, the sealing surfaces of the side plates, i.e., the surfaces which are in sliding contact with the end surfaces of the casting rolls, are also correspondingly larger. The setting devices, which press the side parts or the side plates against the casting rolls to form a seal, must also be designed to meet a higher set of requirements. All these requirements associated with casting rolls with diameters of more than 800 mm make it difficult to replace the side plates quickly and precisely.
The invention is based on the task of creating a strip-casting machine which overcomes the disadvantages of the state of the art and which in particular makes it easier to replace the side plates and thus reduces the retooling time between two casting operations. It should also be possible for the side plates to be positioned with greater accuracy and to be kept heated until casting begins. The side plates, furthermore, should also remain connected to all the supply and detector lines of the monitoring system for side plates of this type during the replacement operations. An essential secondary goal is to improve the accessibility to the casting rolls, especially when the casting rolls are to be changed, and to make it simpler to prevent oxygen from reaching the casting entry and casting exit areas of the casting machine (inertization). The problems associated with rolls with diameters of more than 800 mm and correspondingly larger side plates are also to be solved.
In accordance with the invention, the side plater can be moved downward by the carrier element in a straight line, either vertically or at an angle or along a curve. The carrier element is advantageously designed as a support arm. The support arm can swivel around an axis or move along a curve. Underneath the machine, the side plate on the support arm can be replaced with a new side plate and moved back along the same route to the setting position. It must be kept in mind that the term xe2x80x9csetting positionxe2x80x9d includes all positions of the plate located between the casting position and the replacement position. According to an exemplary embodiment, it is possible in a first step of the operation for the support arm to shift the side plate away from the standard essentially in a horizontal direction, i.e., in the direction of the longitudinal axis of the casting rolls. This shifting of the side plate can occur along a horizontal displacement path which can be, for example, on a plane underneath the casting rolls. In a second step of the movement, the support arm with the side plate can then be shifted downward in a direction essentially parallel to the end surfaces of the casting rolls.
The displacement path can take the side plate to a side plate changing station, which is separated spatially from the casting platform by a wall. Separating the side plate station in this way makes it possible for the following work steps such as cleaning, maintenance, replacement, adjustment, preheating of the side plate, etc., to be carried out in an orderly and clean manner while also preventing accidents.
So that the strip-casting machine can be made narrow in proportion to the width of the strip, it is possible according to another exemplary embodiment for the side plate to be moved downward between the bearing journals or bearing points of the casting rolls. The side plate, with or without the setting device, can be shifted downward between the end surfaces of the roll barrels and the standard. For this purpose, the casting rolls can also be moved a certain distance apart.
The casting machine can be made especially narrow by mounting the setting and positioning devices on the standard and by making it possible for them to be connected to and disconnected from the side plates while the plates are in the setting position.
Regardless of whether the setting and positioning device can be lowered together with the side plate or the setting device remains on the standard during the replacement of the side plate, the side plate can be moved between the setting position and the casting position by the use of a pressure medium and piston-cylinder units. The plate could also be moved by electromechanical means.
After the side plate has been brought into the setting or casting position, it is possible, if desired, for the support arm to be disconnected from the side part. According to an advantageous exemplary embodiment, the support arm can remain connected to the side plate even while the plate is in the casting position.
If the side plate is shifted downward together with the setting device, that is, if the setting device is also mobile, the device requires centering and support surfaces with respect to the standard when in the setting position so that the setting forces can be introduced into the standard.
The side plate changing device consists advantageously of a support arm with a vertical carrier and a horizontal carrier, where the horizontal carrier is usually connected to a stroke device.
So that the various supply media (heating and possibly cooling media, electric power, pressurized media, etc.) for the side plates can remain connected during the shifting operation as well, it is proposed that the horizontal displacement path be provided with a drag chain for the lines of the supply media to the side plates.
To improve the seal between the rotating casting rolls and the stationary side plates, the side plates can be provided with electromagnetic coils to generate an electromagnetic field to help seal the gap.
An additional reduction in the replacement time for the side plates can be achieved by installing two side plate changing devices on each side of the casting rolls. Thus a worn-out side plate can be taken away by the one changing device while the new side plate is brought up into position by the other changing device.